How do I select faces in a row incrementally (as opposed to growing a selection in all directions)?
You probably want Ctrl Shift  Numpad + Select Next Active, which, as far as possible, will use the pattern of relationship between the active element and the previously selected one to predict the next to be selected
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So, for example, if in a face loop, you have selected two adjacent faces separately, the operation will continue to select in the same direction. If you have skipped a face, the selection will continue to skip faces, and so on. Very useful for selecting at intervals.
Ctrl Shift  Numpad - will deselect back down the sequence.